Video games often include input devices which enable a user to control the position or orientation of an animated character. One problem with typical input devices used with video games is that the body movements needed to use a joystick, trackball, mouse or keyboard input to cause an animated character to move on a video display have no direct or intuitive relationship with the resulting movement of the animated character. For example, a user may move his hand forward or press a key to cause an animated figure to walk. These systems, because they are not intuitive, are typically difficult to learn.
Recently, animated characters have also been used in video-conferencing systems. In such video-conferencing systems, a user controls an animated character so that its posture reflects the mood desired by the individual. In particular, such an animated video conferencing system is described in U.S. Patent application Ser. No. 08/169,163, filed Dec. 17, 1993, now U.S. Pat. No. 5,347,306 issued on Sept. 13, 1994, which is commonly assigned with this application to Mitsubishi Electronic Research Laboratories of Cambridge, Mass.. This system also includes an input device which a user wears to provide indications of the positions of parts of the body. Individuals may control movement of an animated character with their own body movements. That is, an individual could move an arm to cause the arm of the animated character to move in a similar manner. There are a variety of these kinds of devices.
One type of such device is the ADL-1, from Shooting Star Technology, of Burnaby, British Columbia, Canada, which is a six degree-of-freedom mechanical head-tracking device. A similar device, available from SimGraphics Engineering in South Pasadena, Calif., mechanically tracks several locations on the wearer's face and displays an animated face whose lips and expressions move in synchronization with those of the wearer.
There are suits or other types of clothing that can be worn by a user to indicate the motions of the joints of the user for body tracking. Examples of these are the CyberGlove, CyberArm, CyberVest, and CyberSuit, all part of a product line called CyberWear body instrument garments from Virtual Technologies, of Stanford, Calif.. A magnetic tracker called FasTrak is available from Polhemus, Inc., of Colchester, Vt., which gives a computer six coordinates that specify the location and orientation of a hand. There are also video tracking systems where the user wears a series of reflective markers or light emitting diodes (LEDs) which are tracked using video cameras.
These devices generally have significant drawbacks. The first is that users are encumbered by having wired sensors directly attached to them or clothing and therefore have limited motion. For example, with one such device, a user wears a helmet and the helmet is attached to a wall via an articulated arm. Users cannot freely walk around or move their hands and head without running the risk of hitting wires, and possibly disconnecting them from the computer. The clothing usually requires assistance to be put on and taken off, and may have to be individually tailored.
In an attempt to avoid these drawbacks, optical systems which perform a variety of image recognition tasks, such as object and motion recognition, eye tracking, gesture recognition, etc., have been used. These systems perform a task similar to that performed by the body language researcher, though in an automated manner. A significant drawback with image recognition systems is that they require computationally intensive processing by a powerful computer, and are therefore expensive. More importantly, the time required to perform appropriate computations results in unacceptable latency. Thus, animated characters controlled by the input device do not track actual movements of the individual, resulting in inadequate performance.
Experts have filmed and video-taped body motions of people in interview situations and everyday communication. They use these recordings for carefully watching and noting body motion to determine how "body language" is used as an additional communication channel. These experts, in a field called kinesics, have created a written language, similar to musical notation, to record body movements in a way that completely communicates the motion of the participant to others in their field. In the past, the only way to record the body motion in writing was to view the film or video tape over and over, taking careful notes of the motions and posture of the participant.
For the purposes of providing further background information, U.S. Pat. No. 5,060,174 describes a chair which is adapted to provide pressure profiles from when an individual is seated in the chair. This system is not used to infer posture, but rather to evaluate the load bearing quality of the seat.